A new simultaneous approach to the steady-state simulation of complex technological systems

1977 ◽  
Vol 42 (12) ◽  
pp. 3570-3575
Author(s):  
S. Ragheb Tewfik ◽  
J. Vrba
Keyword(s):  
Steady State ◽  
Technological Systems ◽  
Simultaneous Approach ◽  
Steady State Simulation

Global steady state simulation of complex technological systems - an unified approach

1980 ◽  
Vol 45 (12) ◽  
pp. 3436-3459
Author(s):  
Josef Vrba
Keyword(s):  
Steady State ◽  
Linear Equations ◽  
Computational Algorithms ◽  
Algebraic Equations ◽  
Global Approach ◽  
Technological Systems ◽  
Unified Approach ◽  
Decomposition Level ◽  
Steady State Simulation

In general, mathematical models of steady state simulation schemas of complex technological processes are formed by sets of algebraic equations. The formal description of global approach to the solution of such sets is presented. The utilization of preliminary solution of linear equations of the set for its reduction and for the expression of dependency of the so-called eliminated variables on the remaining ones, as arguments of the reduced set, (i.e. the first decomposition level) is considered. The determination of disjoint subsystems of the reduced set (i.e. the subsets of nonlinear equations which may be solved serially and independently of each other in a sequence) and the determination of the hierarchy of their solution, when there are several such subsystems, is meant as the second decomposition level. The possibility of including of special models with particular computational algorithms in the equation-like model of complex system and the way of solution of such a problem with the mentioned two-level decomposition is also discussed. The including of both types of decomposition and the solution of the reduced set of equations in common computational block is dealt with.

Cyclic Breathing Simulations in Large Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles

2012 ◽  
Author(s):  
D. Keith Walters ◽  
Greg W. Burgreen ◽  
Robert L. Hester ◽  
David S. Thompson ◽  
David M. Lavallee ◽  
...  
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Large Scale ◽  
Whole Body ◽  
Patient Specific ◽  
Cfd Simulations ◽  
Reduced Order ◽  
Scale Models ◽  
Steady State Simulation ◽  
Conducting Zone

Computational fluid dynamics (CFD) simulations were performed for unsteady periodic breathing conditions, using large-scale models of the human lung airway. The computational domain included fully coupled representations of the orotracheal region and large conducting zone up to generation four (G4) obtained from patient-specific CT data, and the small conducting zone (to G16) obtained from a stochastically generated airway tree with statistically realistic geometrical characteristics. A reduced-order geometry was used, in which several airway branches in each generation were truncated, and only select flow paths were retained to G16. The inlet and outlet flow boundaries corresponded to the oronasal opening (superior), the inlet/outlet planes in terminal bronchioles (distal), and the unresolved airway boundaries arising from the truncation procedure (intermediate). The cyclic flow was specified according to the predicted ventilation patterns for a healthy adult male at three different activity levels, supplied by the whole-body modeling software HumMod. The CFD simulations were performed using Ansys FLUENT. The mass flow distribution at the distal boundaries was prescribed using a previously documented methodology, in which the percentage of the total flow for each boundary was first determined from a steady-state simulation with an applied flow rate equal to the average during the inhalation phase of the breathing cycle. The distal pressure boundary conditions for the steady-state simulation were set using a stochastic coupling procedure to ensure physiologically realistic flow conditions. The results show that: 1) physiologically realistic flow is obtained in the model, in terms of cyclic mass conservation and approximately uniform pressure distribution in the distal airways; 2) the predicted alveolar pressure is in good agreement with previously documented values; and 3) the use of reduced-order geometry modeling allows accurate and efficient simulation of large-scale breathing lung flow, provided care is taken to use a physiologically realistic geometry and to properly address the unsteady boundary conditions.

Performance evaluation of recent procedures for steady-state simulation analysis

2006 ◽  
Vol 38 (9) ◽  
pp. 711-727 ◽  
Author(s):  
Emily K. Lada ◽  
Natalie M. Steiger ◽  
James R. Wilson
Keyword(s):  
Performance Evaluation ◽  
Steady State ◽  
Simulation Analysis ◽  
Steady State Simulation

Model and Algorithm for Thermal Performance Calculation of Power Station Boiler Based on Process Steady-State Simulation Theory

2013 ◽  
Vol 483 ◽  
pp. 587-593
Author(s):  
Hong Kai Liao ◽  
Yue Xi Yu ◽  
Yan Ling Wu ◽  
Wei Zhong
Keyword(s):  
Steady State ◽  
Thermal Performance ◽  
Simulation Theory ◽  
General Purpose ◽  
Thermal Calculation ◽  
Process Unit ◽  
Power Station ◽  
Steady State Simulation ◽  
Power Station Boiler ◽  
Performance Calculation

Thermal performance calculation is the core task of designing power station boiler. By abstracting generalized components and generalized fluid nodes, and defining the process unit and process section at the logic level, the universal physical model of boiler was built in a particular form of flowsheet. Meanwhile, a sequential modular approach was proposed as the main algorithm for boiler thermal calculation based on process system steady-state simulation theory. Two key problems in the algorithm, i.e., module calculations and the logics of calling the modules calculations were explained. Finally, a practically developed system BESS, which has excellent flexibility and extensibility was presented. It turns out that the model and algorithm can be successfully employed in developing the general-purpose software for boiler thermal calculation.

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